1. Field
One or more embodiments of the present invention relate to photovoltaic devices and methods of manufacturing the same.
2. Description of Related Art
A solar cell is a photovoltaic device for converting light, such as sunlight, to electric energy. Unlike other energy sources, solar energy is infinite and is an environmentally friendly energy source, and thus is becoming more and more important. The most basic structure of a solar cell is a diode formed of a PN junction and is categorized according to materials constituting a light absorbing layer.
Solar cells having light absorbing layers formed of silicon may be categorized into crystalline (for example, polycrystalline) wafer type solar cells and thin-film (amorphous, polycrystalline) type solar cells. The most popular examples of solar cells include compound thin-film solar cells using CuInGaSe2 (CIGS) or CdTe, Group III-V solar cells, dye-sensitized solar cells, and organic solar cells.
A hetero-junction solar cell, which is a crystalline solar cell, uses a crystalline semiconductor substrate as a light absorbing layer, and a non-single crystal semiconductor layer having crystallinity different from that of the semiconductor substrate is formed on the crystalline semiconductor substrate to fabricate the hetero-junction solar cell.
A hetero-junction solar cell includes a positive electrode and a negative electrode on a front surface and a rear surface of a semiconductor substrate, respectively. In such a structure, electrodes are arranged on a surface to which sunlight is to be incident, thus interrupting incidence of sunlight.
Furthermore, a hetero-junction solar cell includes transparent conductive layers on a front surface and a rear surface of a semiconductor substrate. Therefore, there is a loss in a light transmitting ratio due to transparent conductive layers, and thus efficiency of light incidence decreases. Furthermore, resistance of a transparent conductive layer is greater than that of the electrodes, thus increasing overall resistance of a solar cell.